The heavy German Cavalry (for by its name they wish to be known, for it carries credit with it), went through here two days since in admirable order, the horses in particular, but the latter are altogether too slight for the men, who are all large, bony, heavy men, of a certain age, and experienced heroes. It will not be easy by a royal order, and light jacket and caps, to transform these gentlemen into light Germans, nor do the corps like it at all. Ponsonby’s heavy brigade is also close by, fresh from Spain, like the Germans, and in the same excellent condition. Nearly ten thousand Spaniards, very fine-looking men, and in good discipline, are also two miles from this, at or near Barcelona. Hitherto they have behaved in general much better than was expected on the march; but we feed them, as they have no transport. If they will but fight a little in return, and take their share of loss, we should do famously.

Murillo’s Spaniards, I am sorry to say, have begun very ill in our front. The day before yesterday, Soult made an advance against them; when they were ordered to fall back a little to a rivulet, and there defend themselves. Once with their backs turned, however, away they went, and never stopped until the Buffs were ordered up to stop the French, who, the moment they saw the red coats coming on, were off home again very quickly, but not quite so rapidly as the Spaniards had run from them.

The Portuguese cavalry had a little affair, and behaved well. The 14th Dragoons had also an affair the day before yesterday. Half a squadron under Captain Babington were ordered by Colonel Harvey to drive off a French half squadron, and then halt until he came up. They upset the French, saw another whole squadron beyond, were tempted to go on by their first success, and succeeded in a great measure again, but Captain Babington was taken. The wounded French dragoons of the 5th regiment, brought in here prisoners, are all very fine men, and the whole regiment are said to be the same sort of men. They came in much cut about the head and hands.

The forage animals of head-quarters were yesterday very nearly getting into a terrible scrape—about two hundred and fifty animals, and two of mine in the number. They foolishly went in front of our picquets, or nearly so, though regularly under commissariat directions. Whilst they were loading at a farm, one peasant slipped away, and it is concluded told some French dragoons near what was going on, whilst the other in the house gave some of the party wine. There were four artillerymen unarmed in the house, and about six Portuguese, one of whom was mine, when a French officer of cavalry, with his sword drawn, came to the window, told them all to come out, and that they were prisoners. When they came out, seeing that he was alone and his party three or four hundred yards off, they mounted their mules, and nearly all got off, with the loss of, it is said, only one man and two or three mules. Some fellows galloped all the way here without their loads or cords, and at first spread an alarm that all were taken. They arrived home in the course of the day, and my Portuguese brought home a load of good hay and two deserted ropes in triumph. It is thought that the party should have brought off the officer prisoner, but most are satisfied with having got their own property back again. He cut one of the artillerymen on the finger, who put up his arm to save himself.

Another party of muleteers with stores from Mont de Marsan to Bordeaux, with supplies for the seventh division, to which they belonged, were attacked three days since on their road near Roquefort, quite in our rear and on our communications, by some French partizans, a sort of guerillas called La Bande. These now, it is said, are employed by Soult: they were formerly a set of douaniers, or smuggler catchers. Several mules were killed and wounded, and, I believe, some muleteers killed, and some of the money taken. It is to be feared that the Spanish muleteers will begin to be alarmed at this. We have cavalry, however, on the road, and they will now be more on the look out in future.

This place is now much crowded. Three new Generals came in yesterday and to-day,—Sir Stapleton Cotton to-day, with, about a hundred animals belonging to himself and his staff. I was turned out of my stable in consequence, though but a very bad one, and my animals are now in a back kitchen turned into a stable. At Barcelona the Spaniards turned out the cavalry with much less ceremony. It is said that a company, with a Captain at their head, gallantly charged Captain S——’s horses and bâtmen (General C——’s aide-de-camp), and were very successful. One little blood-horse kicked about, broke loose, and made a good defence, without injuring himself; but another horse, not so quick in his retreat, received two slight bayonet wounds, and a slight cut with a sabre, and the Spaniards carried the day, behaving like heroes!

Our people are all moved in consequence, and I hope that these valorosos and blood-thirsty gentlemen will soon be allowed to contend with a more glorious enemy, and will behave with equal spirit when the opportunity shall arrive.

The Swedish (Bernadotte’s) aide-de-camp is, it seems, to campaign with us; he is buying horses, &c., and preparing for the field. He is a great talker, and, I understand, of this country. From his conversation he seems to have served against us under Massena in Portugal, but how he is what he is I do not exactly understand.

The weather is still very cold. Lord Wellington would not even condescend to-day to go and look at the French. He only sent Colonel Gordon to go on to Gartin, and report.

Head-Quarters, 17th March, Aire.—About three o’clock yesterday we learnt that the French were off, and filed through Conchez, apparently on the way to Tarbes. I think they will not venture to go too near the mountains, but must make for Toulouse. If not, our fourth division, which, it is said, will be here to-night, will make us strong enough, I hope, to push a column through Auch straight to Toulouse, while the rest follow Soult, and we should then be at Toulouse first. I conclude he will turn that way from Tarbes. General Hill moved a little after the French yesterday to keep them in sight. The rest of the army will, in my opinion, get in motion to-day or to-morrow, and head-quarters move on very soon afterwards. About fifty prisoners were sent in here last night, mostly dragoons.